You deserve a daily dose of good news. For the latest in science and the night sky, subscribe to EarthSky’s free daily newsletter.
Did the sun swallow a planet early in its history?
The early days of solar system formation were chaotic! For example, planetesimals – solid bits ranging from a few hundred meters to hundreds of kilometers across – smashed into each other and clumped together to form planets, or they flew apart. And a planet-sized body appears to have hit Earth to become the moon.
And some of the early solar system’s turbulent motions likely involved material spiraling into the sun as well. On September 10, 2026, researchers said a super-Earth-sized planet might have fallen into our sun billions of yeas ago. It might have left behind a chemical fingerprint inside the sun that scientists can see today.
The researchers published their peer-reviewed study in the journal Monthly Notices of the Royal Astronomical Society on September 10, 2026.
Fingerprints from a lost planet
Lead author Mutlu Yildiz of Ege University in Turkey said:
Our new study suggests that a planet several times more massive than Earth may have fallen into the young sun and left a lasting chemical imprint deep inside it.
As the planet got pulled into the sun’s environs, the researchers said it could have even survived as it enters the sun’s outer atmosphere. As in, the planet would still have been mostly intact and lost very little mass as it first began to merge with the sun. Therefore, the planet might have left behind “fingerprints” before the sun completely consumed it.
Can eating a planet explain solar puzzles?
Solar researchers have long been puzzled by the sun’s lack of lithium on its surface. Also, their models don’t accurately show all helioseismic observations. For example, the physics models struggle with things such as how deep the convection zone is on the sun, estimated at 125,000 miles (200,000 km) deep! Could the sun eating a planet explain these issues? Yildiz said:
By modeling the sun’s evolution and comparing the results with precise observations of its interior, we find that the ingestion of a super-Earth could help explain long-standing differences between standard solar models and observations, including subtle changes in the sun’s internal structure and its depleted lithium abundance.
We were interested in whether these problems might have a common origin in the early chemical history of the sun. Young stars are surrounded by protoplanetary disks, where substantial amounts of material can move between the disk and the star. Since planets are made of material that is chemically different from the gas in the disk, we wondered whether the early engulfment of a planet could have left a chemical signature inside the young sun.
Testing an idea
To test their idea, the researchers used an open-source code, the MESA stellar-evolution code. The researchers investigated a variety of parameters. They looked at how much material the sun would need to consume in order to come up with what we see on the sun today. They also tested alternate theories. And what they ended up with that best fit observations was a scenario in which a super-Earth (some 5–10 times the mass of Earth) fell into the young sun.
What’s fascinating is that the swallowed super-Earth model explains a number of the puzzles we see on the sun. Those include the depletion of lithium and observations of its interior. Yildiz said:
We thought planetary engulfment might affect the solar structure but did not expect the calculations to converge on such a specific super-Earth mass range. That was one of the most interesting outcomes of the study.
Even so, the researchers caution that it’s probably not possible to prove the sun swallowed a planet. But they do hope other researchers will find other observations to bolster their theory.
A missing super-Earth
Super-Earth-type planets seem to be relatively common in the galaxy. With more than 5,000 exoplanets now known, some 30% of them are super-Earths. So where is our solar system’s super-Earth if they’re so common? Perhaps the answer is that it’s now part of the sun.
Previous research has suggested that:
… one or more super-Earths could have formed inside the orbit of Mercury and migrated inward through the gas disk, potentially falling into the young sun.
Yildiz said:
The earlier work proposed that a super-Earth could have formed and migrated into the young sun. Our paper asks whether the sun itself could still carry observable evidence that such an engulfment actually happened, and we believe it could.
The next step is to see if these fingerprints can be independently detected.
Bottom line: Did the sun swallow a planet early in its history? Models show a super-Earth might have spiraled into the sun and left behind a fingerprint we can still see today.
Source: Planetary engulfment as a solution to solar-model discrepancies and its implications for planetary systems
Via Royal Astronomical Society